Referring to FIG. 1, a conventional Gilbert mixer includes a load circuit 1 that is used to receive a direct current (DC) bias voltage (Vdd), and a mixing circuit 2.
The mixing circuit 2 includes a current source 21, a transduction unit 22 and a mixing unit 23.
The current source 21 is used to modulate a total bias current flowing therethrough. The transduction unit 22 is coupled between the current source 21 and the mixing unit 23, and is used to receive a differential intermediate frequency (IF) voltage signal pair that consists of positive-phase and negative-phase IF voltage signals. The transduction unit 22 is operative to allow a differential IF current signal pair to flow into the current source 21 therethrough based on the differential IF voltage signal pair. The differential IF current signal pair serves as the total bias current, and consists of positive-phase and negative-phase IF current signals (I11, I12). The mixing unit 23 is coupled between the transduction unit 22 and the load circuit 1, and is used to receive a differential oscillating voltage signal pair that consists of positive-phase and negative-phase oscillating voltage signals. The mixing unit 23 is operative to allow, based on the differential oscillating voltage signal pair, a differential radio frequency (RF) current signal pair flowing through the load circuit 1 to flow into the transduction unit 22 therethrough. The differential RF current signal pair consists of positive-phase and negative-phase RF current signals (I21, I22), and serves as the differential IF current signal pair.
The load circuit 1 outputs a differential RF voltage signal pair based on its impedance and on the positive-phase and negative-phase RF current signals (I21, I22). The differential RF voltage signal pair has a frequency which is a sum of those of the differential oscillating voltage signal pair and the differential IF voltage signal pair.
In such a configuration, upon DC analysis, since the current flowing into the transduction unit 22 flows entirely through the load circuit 1, power consumed by the load circuit 1 is relatively high. In addition, the conventional Gilbert mixer typically improves its self-conversion gain by increasing its power requirements. As a result, the conventional Gilbert mixer may have a further increased power consumption. In other words, the conventional Gilbert mixer cannot obtain a high conversion gain at low power consumption.